按層順序列印二叉數

public class BinarySearchTree {public Node root;public void insert(int value){root = insert(root,value);}public Node insert(Node node,int value){if(node == null){node = new Node(value);}else if(value <= node.value){node.left = insert(node.left,value);}else{node.right = insert(node.right,value);}return node;}public void print(Node node){if(node != null){print(node.left);System.out.print(node.value+" ");print(node.right);}}public void printByLevel(){LinkedList<Node> list = new LinkedList<Node>();list.push(this.root);while(list.size() != 0){int length = list.size();for(int i = 0 ;i < length; i++){System.out.println(list.get(i).value);}for(int i = 0; i < length; i++){if(list.get(i).left != null)list.offer(list.get(i).left);if(list.get(i).right != null)list.offer(list.get(i).right);}for(int i = 0; i < length; i++){list.poll();}}}public static void main(String[] args){    int[] a = {6,4,9,3,1,8,2,7};    BinarySearchTree b = new BinarySearchTree();        for(int i = 0; i < a.length; i++){    b.insert(a[i]);    }    //b.print(b.root);    b.printByLevel();}}class Node{public int value;public Node left;public Node right;public Node(int value){this.value=value;left=null;right=null;}}